Well, obviously all intelligent devices have a far superior version of Google Translate installed onboard, and it will automatically update too. Untick the update box so it will stop annoying you to update every week.
As for why everyone can understand English, that is just a
ingrained sci-fi trope for the purposes of simplification.
But seriously, there are most likely ENGLISH words that I don't know of, and reading something from merely 100-200 years ago would probably require me to look some things up. And every language has some nuances that don't translate very well.
And this is to consider numerous dialects that can pop up that can give words entirely different uses.
And with the tools at hand, there is no reason to not spend extra effort into translating stuff.